Just exit instead of asking the application to quit when the connection goes down.

As discussed in abe1be628da687b1943a41e5411f34f646aeca86, the existing approach
is ineffective in some cases in that it merely requests that the application
shut down. In the case of misbehaving threads (for example), the application can
sit around indefinitely instead of quitting as it should.

Additionally, add a warning to make it clear what happened.

This also matches up with the xcb plugin's behavior.

Change-Id: Iabc17dc268c849635263a16754b9f3bfa7bd9e4a
Reviewed-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>
Set window state on platform window creation

When creating the platform window, the window state should be set
according to the value in the associated QWindow. This is especially
important for new QWindows, as the application may expect the compositor
to resize e.g. maximized or fullscreen surfaces.

Change-Id: I9cf4eb810bb4fa6305da4206c9a2cec0247c2fe6
Reviewed-by: Jan Arne Petersen <jan.petersen@kdab.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>
Constrain window geometry

It is the platform plugin's responsibility to constrain window geometry
to QWindow::minimumSize/QWindow::maximumSize. Platform subclasses should
make sure to call the setGeometry() base method first to make sure
geometry() has been constrained before continuing to resize surfaces.

Change-Id: I1c25ba6a32a3597603a3ffdb799b4e22b9d8f3ec
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>